Production of wood fiber



Feb. 21, 1961 c. c. HERITAGE 2,972,171

PRODUCTION oF woon FIBER Filed Oct. 4, 1952 4 Sheets-Sheet 1 IN V ENTOR. C/a Ik C Her/'czje A T TORNE Y' Def/'bm for Feb. 21, 1961 c. c.HERITAGE PRODUCTION 0F woon FIBER 4 Sheets-Sheet 2 Filed Oct. 4, 1952/Ndf NTE/R' /ar/f C Her/'gge T rDRA/D/E Feb. 21, 1961 c. c. HERlTAGE2,972,171

PRODUCTION oF woon FIBER Filed Oct. 4, 1952 4 Sheets-Sheet 3 IN V ENTOR.

Y i Clark C. Herage BY Mm/ ETT/:www5

Feb. 21, 1961 c. c. HERITAGE PRODUCTION oF woon FIBER 4 Sheets-Sheet 4Filed OC'b. 4, 1952 IN V EN TOR clark C. Hering@ BY HTT/:IRNQ/E UnitedStates Patent@ PRODUCTION F WOOD FIBER Clark C. Heritage, Tacoma, Wash.,assigner, by direct and mesne assignments, of one-half to WeyerhaeuserCompany, a corporation of Washington, and one-half to Wood ConversionCompany, St. Paul, Minn., a corporation of Delaware Filed Oct. 4, 1952,Ser. No. 313,098

9 Claims. (Cl. 19-72) This invention relates to the manufacture of woodfiber and has particular reference to the fractionation, in the absenceof suspending water, of wood ber exhibiting a broad particle sizedistribution, into new and useful bulk ber products.

Wood ber for different purposes is produced in many different ways. Thevarious processes may be classified in a general way as Wet processes,dry processes, and moist processes. The wet processes may employattrition mills, but in general they are characterized by a cookingstage in which chemical action usually plays an important part. Such acooking stage usually employs a batch type process, as distinguishedfrom a continuous production process, in which the source material forthe ber is submerged in an aqueous solution of the reagents. This typeof process is generally employed by the paper industry and the productis referred to as pulp. The purpose of the cooking stage is to removenon-cellulosic materials from the wood and free the ber thereby. When aso-called chemical pulp is produced, substantially all the lignin isremoved; when a .so-called semi-chemical pulp is produced, only aportion of the lignin is removed. Sulfate and sulfite pulps are examplesof chemical pulps.

Fractionation of wet process ber is accomplished by the use of flat orcentrifugal screens at very low consistency, usually followed bythickening of the aqueous suspension. This type of process produces ahigh quality, uniform ultimate ber, but it has many disadvantages forcertain purposes, among which are the loss of valuable solubles from theber, high capital cost of the plant, and high operating cost. Anadditional disadvantage for some purposes is, the water logged conditionof the ber.

The present invention may be applied to a we t process ber by predryingthe ber, but the invention has its greatest utility and advantage inconnection with the use of ber which has never been suspended in Water.

The dry processes are identified primarily with wood flour asmanufactured for certain special purposes and sander our which isproduced as a by-product in ply- Wood mills and the like. Theseprocesses involve a harsh dry abrasive action which does not produce anacceptable whole product where brous characteristics are desired. Theindividual particles include a considerable portion of minute chunks ofwood in addition to a useful ber content. The present invention providesa means of separating such useful ber content from the less desirableparticles.

The third type of process, illustrated and described in detail herein,is the so-called moist process. lt is recognized in the art that usefulber cannot be made from green chips by attrition without some treatmentof the chips such as aqueous soaking with or without chemy icals,steaming, or both. The moist processes include such a step as apretreatment stage in a continuous process which is of short duration incomparison with the cookingtime required in the` batch type wetprocesses.

2,972,171 Patented Feb. 21, 1,961l

lCC

The source material for wood ber by the moist process may vary in sizefrom chips to sawdust-and may be green or dry, although dry wood is notordinarily employed in commercial production.

In a moist process the pretreatment and attrition stages may be combinedin one continuousqpressure machine.v Examples are the Asplund debratorwith or without anV extended preheater, the Beveridge-Kehoe Chemi-pulperused with the Asplund machine in place of the Asplund-- preheater, andthe Messing Durkee digester in combination with an Asplund debrator inplace of the-Asplundf preheater. closed in the Asplund Patents No.2,008,892 and No. 2,145,851. The Beveridge-Kehoe apparatus isdisclosedin the Beveridge and Kehoe Patent No. 2,323,194. Anextendedpreheater for the Asplund defbrator is disclosed in the Lowgren et al.Patent No. 2,396,587.

The two steps of the` moist process may also be carried out in separateapparatus where the pretreatmentJ stage is separated from the attritionstage so that theattrition machine may be operated at atmospheric pres,-sure. In such cases, the pretreatment stage may utilize variousequipment which is well known in the art, such as the Plywood ResearchFoundation Steamer, the Beveridge-Kehoe Chemi-pulper, the Messing andDurkee dir- A gester, or it can comprise merely a simple preimpregnationtreatment. Source material from any of the foregoing pretreatmentdevices-may be debered in such at-r mospheric pressure attrition devicesas the Bauer machine, the Sprout-Waldron machine, the Prater machine,which is an impact machine of the hammer mill type, orthe Allis-Chalmersinterplane grinder. The latter is i1- lustrated in the Marsh Patent No.1,762,122.

There is a commercial demand for largequantities of ber of high qualityat low cost. As was hereinabove` pointed out, the quality of a dryprocess whole productl such as wood our and sander dust is notacceptable, where some reasonable ber length and felting prrope'rtiezsYare desired. The wet processber may be produced `to* any desiredstandard in regard to particle size, but some' or all of the watersolubles are lost in the processing..- Also, the wet process is toocostly for many uses YwhereA it is in competition with conventional lesserpensivema-F terials, by virtue of the procurement, handling anddisposal of huge quantities of water.

The moist processes, therefore, offer attractive promise of a low costhigh quality ber in suicient quantityto satisfy the demand. The process`is continuousI and the capital and operating costs are moderate, asmall kplant being capable of relatively large output.v Further, someofthe moist processes may be controlled to prevent loss of the valuablewater soluble content of the wood. These' solubles are principally theproducts of hydrolysis ofthe most easily hydrolyzed portions of the Woodand the water soluble organic bodies possess useful thermoplastic andbonding properties. Fiber containing these solubles is hereinafterreferred to as whole wood ber.

The chief objection to the moistprocesses as conventionally practiced isthe wide range of particle size distribution. Y The particles may varyin size from broken individual bers to rather large ber bundles, sticksand" ribbons approaching the coarseness of fine excelsioig` There isneed in the industry for a higher quality and more uniform ber of themoist process ytype in aninter` mediate range of coarseness having'alimited amountof fines and no large ber bundles, sticks or ribbons.' u

Analysis of Asplund ber reveals that it consists of:

(a) partially attritedchips which are called sticks,

The Asplund process and apparatus` are disbundles. The word lines asused in the preceding paragraph, referring to size only, could meansmall tracheids, broken larger tracheids, or broken short ber bundles ofthe nature'of fine sawdust. The tracheids in Dougles tir are of varioussizes, averaging about I; inch in length aud 0.002 inch in diameter butvarying widely depending upon age and position in the tree.

Y Many large volume uses to which moist process liber are put requireparticle sizes ranging from those sizes resembling pulp to those sizescomprising slender flexible bundles of tracheids which behave insubstantially the same manner as individual tracheids. Such a desirablefraction will then contain only a limited amount of broken or shortenedsingleV tracheids and broken bundles, and no partially attrited chips ortiber bundles exceeding a certain predetermined size. Heretofore, highquality liber having these desirable physical characteristics has beenobtainable only by the expensive Wet processes practiced by the paperindustry and has not been obtainable by the convenient and lessexpensive moist processes. Fiber having the desired physicalcharacteristics in combination with the useful soluble content of theWood from which it was derived has not been obtainable.

Objects ofthe present invention are, therefore, to provide an improvedhigh quality whole Wood liber, to prov ide a moist process liber ofcontrolled particle size distribution, to provide a stick free moistprocess liber, to provide an improved process for refininglignocellulose liber,Y to provide an Vimproved process for controllingthe particle size distribution of liber, to provide a process forproducing a'plurality of liber products having diierent predeterminedparticle size distributions, to provide a novel liberfractionationprocess, and to provide apparatus for carrying out theprocess and producing the prod-V tail hereinafter. When the sourcematerial is produced byV a dry process, such as wood our and sanderdust, it does not contain particles large enough to be classed assticks, ribbons or large liber bundles, and themost valuable fractioncomprises the coarse material. In such case the Y fractionation step iscontrolled to separate the particles having individual libercharacteristics from the very line A'dust in which the particles do notexhibit liber characteristics.

l When the source material is produced by a moist process thefractionation is controlled to reject the coarseV material, the desiredliber characteristics being found then in the liner particles. VSuchfractionation can be made particularly effective by controlling thedetibering apparatus to minimize the very line particles which lackliber characteristics.

-/Therinvention is hereinafter described in greater detail withreference to an Asplund type delibrator as illustra- Vtive of a moistprocess for the production of lignocellulose liber., In the process andapparatus of the Asplund patents, wood chips are introduced into a highpressure so'- called inert gaseous environment providing a temperatureabove 212 F. at which the lignin content of the wood is softened topermit ready delibration by mechanical means. The chips quickly softenand are fed to a rotary deiibering d isc mechanism housed in saidenvironment which Imechanically rubs the softened chips to elect thedelibering thereof. As stated hereinabove, the desired ber fraction isaccompanied by a certain amount of less desirable line. and coarsematerial. Under optimum conditions of feed rate, condition of theYdiscs, disc adjustment, temperature,` pressure, etc., for a particularwood, a fairly good 'quality' of liber is produced forV certain roughuses,

4 Y comes less exact, and taking into consideration possiblefluctuations in the feed rate nand other variables of the machine, thequality of the fiber in practice is usually considerably below thedesired standard, especially in regard to the inclusion ofcoarsepmaterial. Another factor affecting the quality in production alsoinvolves the feed rate, o

even though feed .is maintained fairly constant. The liber tends to beof a higher and more uniform quality, that is, with fewer large fiberbundles, sticks and ribbons at an uneconomically low feed rate. Thepresent invention provides for fractionation of the defibrator output sothat the feed rate may be raised to an economical production levelWithout sacrificing the quality of the ultimate product. In otherwords', with fractionation there isan optimum equilibrium conditionwhich yields a higher output of usable liber.

The defiberated Wood is discharged from the Asplund machine through thereciprocating valve arrangement disclosed in the Asplund patents. .Thepretreatment and delbering stages may take place in from 0.5 to 30minutes, depending upon the duration of the pretreatment stage and theequipment provided to carry it out. y o

v An advantage of the Asplund type defibrator is the gaseousenvironment, preferably steam, surrounding the wood before, during andafter delibration, wherebyY the material is carried through the processinthe absence of suspending` liquid.V Where water suspensions Vareemployed in preparing the liber, a substantial fraction of the originalwood substance is lost by dissolution in the Water. This materialcomprises one or more substances derived from the original wood such asthe simplest forms of lignin, polysaccharides and other organicmaterial. The material so removed has liber bondingV and other desirableproperties, and its loss from the liber requires the use of replacementbonding material for certain purposes such as hot pressed fiber boardsand hot pressed molded articles. l

v Fiber produced by the Asplund type process preserves virtually (somevolatiles are lost to the atmosphere) all the Water soluble content ofthe fibers. This includes that of the natural Wood and more vwhich isformed in the process of delibering as an incident tothe steamenvironment in the pretreatment and delibering stages as explained inthe priorV Heritage Patent No. 2,553,412. As explained therein andhereinabove stated, the Water soluble content, especially the formedwater solubles, contain polysaccharides and lignin, For convenience, bercontaining'the natural water soluble contentrof the wood and the formedwater solubles is defined as whole wood fiber or product to distinguishit from a wood liber or product from which some of the natural or formedWater solubles have been removed.

One of the characteristics of the Asplund machine is that it dischargesmoist tiber ina loose, substantially untelted condition which may beeasily and directly dried. The steam pressure at discharge from themachine may be used to convey the liber in a conduit for drying actionwithout subjecting it to conditions which would destroy its'substantially unfelted form. Avoidance of wetting the iiber to thepoint of matting-and avoidance of suspending it in Water are botheconomically important for the additional reason that wetting producesclotting, which requires unfelting with possible injury or breaking ofthe fibers. Wetting of the ber also exhibits other elects which changethe physical properties ofthe iiber, such as the felting and elasticcharacteristics, thermal conductivity, free footage or density, etc.` Insummary, for `the purpose of the present invention it is desirable,therefore, that the fiber be formed and handled in the absence ofsuspending or clottingrwater, and that it be dried directly from itsoriginal loose and liuffed condition;

In the drawings: Y

YFigure lis a schematic diagram of apreferred plant organization forcarrying out Vtheptocess of thel linvention wherein the fractionationstep is effected in a rotary air separator;

Figure 2 illustrates an arrangement of two mechanical fractionatingseparators in series;

Figure 3 illustrates a winnowing chamber for dry fractionation;

bFigure 4 is a photomicrograph of Asplund Douglas fir Figure 5 is aphotomicrograph showing a fine fraction of Asplund Douglas fir fiber;

Figure 6 is a photemicrograph of a coarse fraction of Asplund Douglasfir fiber; and

Figure 7 is a photomicrograph of kraft pulp used by the paper industry.

Referring now to Figure 1, the lignocellulose source material such aswood chips is delivered to a chip bin 10 in a moist state. By this ismeant a state characterized by the absence of free water surrounding thechips. No effort is made to dry the chips; they preferably have themoisture content of the source material which is ordinarily green millends and other sawmill leftovers free of bark. Such material usually hasa moisture content suitable for debering in the Asplund type machine. Ifthe source material contains more than the amount of moisture tosaturate the fibers, the excess moisture will be squeezed out in thecompression or plug forming section of the Asplund machine, and, if itis drier than fiber saturation, the moisture content is increased by theintroduction of water in addition to the steam which is used in anyevent. The addition of water is restricted to an amount suicient to aidin the satisfactory defibering of the source material but insucient toproduce a continuous solubilizing phase.

The Asplund type defibrating machine, indicated generally at A,comprises a plug forming or compression chamber 11, a receiver 12, adefibering disc housing 13, and a discharge connection 16. In theoperation of the machine, chips are forced into the plug forming section11 under great pressure and are compacted together to form a plugcapable of holding a substantial steam pressure in the receiver 12 andhousing 13. Steam is introduced through steam pipe connections, notshown, at a rate sufficient to maintain the desired steam pressure whilesteam and fiber are being discharged continuously at high velocitythrough the discharge connection 16.

The steam escaping from the discharge connection 16.

carries the fiber through a duct 30 to a steam separator 31, from whencethe steam escapes to atmosphere, and the ber drops onto a reversibleconveyor belt 32 (see U.S. Patent to Heritage, No. 2,405,213). When theconveyor belt travels to the left it discharges the fiber into a chute33 communicating with a duct 40 through which heated air is propelled bya blower 36. Duct 40 constitutes a first drying stage in which the fiberis air borne to a cyclone separator 41.

The intake side of the blower 36 is connected through pipe 42 to a firststage heater H1 having steam pipes to heat the air passing therethrough.Heater H1 is supplied in part by a fresh air supply pipe 44 and in partby a recirculating air pipe 45. Pipe 45 connects with the lair dischargesection of cyclone separator 41 whereby a portion of the air fromcyclone 41 returns through pipe 45 to heater H1 and blower 36 forrecirculation and a part is discharged to atmosphere through outlet 46.Thus the inlet 44 constitutes a fresh air makeup to compensate p for theloss at 46.

The moisture thus removed from the fiber escapes to vatmosphere alongwith the air lost at 46, this quantity of humid air being constantlyreplaced by a similar quantity 'of relatively dry air at 44 at ambienttemperature and humidity. The partial drying of the ber in duct 40 priorto fractionation is a desirable expedient to facilitate fracdonation,but is not necessary to the invention.

Cyclone separator 41 discharges the fiber into a mechanicalfractionating separator B. This separator is of the general typedisclosed in the Crites patent, Re. 20,543, issued November 2, 1937. Thedefibrator fiber delivered to the separator contains a minor quantity ofsticks and fiber bundles, in addition to the ultimate wood fiber whichis desired in a relatively pure state for many uses. The reversible belt32 may be driven to the right to deposit the fiber from steam separator31 directly into the separator B, by-passing the first stage drying duct40, but the moisture content of the ber is usually such that if it isgiven a partial drying treatment through the first stage drying duct 40the separator B will operate at a higher feed rate and effect a betterseparation of coarse and fine fractions. The desired fine fraction isdeposited in an outer cone 50 having a chute 51 leading to a seconddrying stage 55. Drying duct 55 is supplied with hot air from a blower56 to convey the fiber in the air borne passage to a cyclone separator61. The inlet of blower 56 is connected through a pipe 62 to a secondstage heater H2. Heater H2 is supplied with air in part through a freshair inlet 64 and in part from a pipe 65 connecting with the airdischarge section of cyclone 61. Cyclone 61 thus recirculates a portionof its air through pipe 65 and vents another portion to atmospherethrough outlet 66. Inlet 64 constitutes a fresh air makeup to supply theloss through outlet 66 whereby the moisture removed from the fiber inthe second drying stage -is eliminated from the system.

The separator B subjects its feed material while suspended in air to thecombined influences of gravity, centrifugal force, air currents, andmechanical impacting to separate or classify the material into twodistinct fractions on a coarseness basis. Means of adjustment areprovided in the mechanism to control the ratio of the two fractions soas to produce a fine fraction comprising ultimate ber and slenderflexible fiber bundles, and .a coarse fraction comprising sticks,ribbons and fiber bundles which exceed a predetermined particle size.The tine fraction has a soft, Wooly texture, the coarse fraction, whichhas a rough texture andA shredded appearance, drops into an inner cone,not shown, having a discharge chute 72.

In accordance with the principles of the invention, the coarse materialdischarged from chute 72 is subjected to a secondary refinementtreatment to reduce it substantially to ultimate fiber similar to thatcollected by the outer cone 50. The apparatus for accomplishing thisadditional treatment may be any type which rubs the moist coarseparticles apart with the minimum of breakage, as for example, discattrition mills, ring-roll mills or Mullers. Also, the secondaryrefinement may be effected by returning the coarse material to theoriginal defibrator. One device found to be advantageous comprises aninterplane ref-incr C of the type disclosed in the U.S. patent to Marsh,No. 1,762,122, issued June 3, 1930. In the interplane refiner the coarsematerial from chute 72 is introduced between a pair of horizontalcompanion stationary and revolving attrition discs wherein the refinedmaterial is discharged from the peripheries of the discs into an annularhousing having an outlet pipe 73. The spacing of the grinding discs isadjustable to produce the desired degree of defibering. Outlet pipe 73branches into a duct 74 communicating with the suction pipe 42 for theblower 36 and a duct 75 communicating with the suction pipe 62 of blower56. Duct 74 may be closed by a blast gate 76, and duct 75 may be closedby a blast gate 77. When the gate 76 is closed and gate 77 is opened,the fan suction in pipe 62 will draw the fiber discharged from refiner Cthrough the ducts 73, 75 and 62 and discharge it through the secondstage drying duct 55 to cyclone separator 61 along with the tinefraction introduced from chute 51.

' 4S'When st'illfur'ther separationan'd rnementcarenecessary, gate 77 isclosed and; gate 7.6 isopened. Thenthe suction of blower 36 draws ytheoutput of refiner C through ducts 73, 74and 42 and discharges it'through 'the vfirst stage drying duct 40 along with fresh fiber fromchute 33 to cyclone separator41. The material may thus Ybe recirculatedthrough the separator B and Vany remaining coarse fraction defibered bythe refiner C. Or the 'refined coarse portion may have its ownseparator.

The product conveyed to cyclone separator @iV is deposited on conveyorbelt 80 for finalidisposition. Final disposition may involve merelypackaging for shipment or conversion of the fiber to otherA products.

As illustrative of the functions performed Vby the first 'and seconddrying stages comprising the ducts 40 and 5S Vand their associatedblowers and heater, the defibrator fiber may'enter duct 40 fromthe'steam separator 31 at a moisture content in the neighborhood ofr50%total weight basis. It is found that the` defibrator A does not operatesatisfactorily when the moisture content of the product discharged fromthe steam separator 31 falls below 40% total Weight basas. On the otherhand, the mechanical fractionating separator B operates more efficientlyat a moisture content below 40% total weight basis. These inconsistentrequirements are satisfied by a sufficient margin in the present systemby the moisture content adjustment effected by the first drying stage.The first stage drying duct 40, including the drying action of thecyclone separator 41, preferably reduces the 50% moisture content of thedebrator fiber to approximately 30%. Before disposition of the finalproduct, it is desirable for many uses of the fiber to remove most ofthe remaining moisture in the second drying stage, comprisling dryingduct 55 and cyclone 61, to leave the product.

with a final moisture content of about -l0%. The foregoing values aremerely illustrative, Vand it will be apparent to persons skilled in theart that the present system allows for ample adjustment of the dryingaction in both the rst and second drying stages to hold the moisture Ycontents to the optimum values for a particular source `material andtaking into considerationrthe nature of the additive, if any, introducedat the defibrator and the intended use of the fiber.

The photomicrographs in Figures 4-7 are reproduced to a uniformmagnification of twenty diameters on the original Bristol board drawingsof the patent application whereby the magnification is reduced to aboutthirteen diameters in the printed patent. The specimens are typical butbecause of the small amount of material included in the field of viewthey do not illustrate the true relative amounts of the differentparticle sizes on aV quantitative basis, nor do they'necessarily includethe extreme maximum particle size which may be present only ininsignifi- Ycant amounts in each class of material.

Figure 4 is a photomicrograph of Asplund Douglas fir Yfiber obtainedfrom the defibrator A in Figure l. AThe material included in thespecimen' of the photograph will be observed to contain relatively rigidand massive sticks a, slender flexible bundles of fibers b, individualtracheids c, broken or'shortened single tracheids d, and broken fiberbundles 'e.

Figure 5 is a photomicrograph of a 4fine fraction separatedfrom theAsplund fiber of Figure 4 by dry or .moist fractionation. In thisspecimen it will be observed. first that there are no massive and rigidstickscorresponding to a in Figure 4 nor broken bundles of a size andmassive form comparable to thoseindicated yat e inFigure 4. The specimenin Figure 5 consistsessentially of individual tracheids c, broken orshortenedsingle tracheids d, and 'slender flexible -bundles of fibers b.All of these particles 'have desirable fiber characteristics for feltingand other `purposes.Y This fraction has a uniformly soft and Woolytexture which is readily distinguished from the original Asplund'tiber'shown in 4Figure 4 by its physical appearance and feel .agave/m1-fFiguref' isa photomicrographof a'coarse fractionlseparated from theAsplund fiber of Figure 5 byrdry fractionation. 'Ihespecimen displaysall'the different particle classifications enumerated in Figure 4, butin a larger sample they are found to be present in quite differentproportions on a quantitative basis. The materialin Figure 6 is quitedistinct'from those in both of Figures `4and 5, as the sticks apredominate over all the other particle types and sizes, giving thematerial a rough appearance and texture quite comparable-to conventionalexcelsior. The finer-material appearing in Figure 6 is not present insignificant amounts in larger samples. This coarse Vfraction distinctlydoes'no't have fiber characteristics suitable for felting and likepurposes. The predominating particlesfare thick and Ystiff and comprisemostly sticks, ribbons andA relatively massivebundles, as designated-ate.

Figure 7fis Va photomicrograph of typical kraft pulp. This specimen ischaracterized by the absence ofsticks a and broken bundles .e. Thematerial consists almost entirely lof individual tracheids c and brokenor shortened single tracheids d, with a small proportion of apparentlyslender flexible bundles of fibers b consisting o-f a small number ofindividual'tracheids. The slenderness and `flexibility of practicallyall the particles imparts Vthe typi- -cal ber characteristic which isextensively utilized in Vthe making of paper and for other purposesrequiring uniform fiber characteristics in the particles. This materialaffords a fair illustration of the goal of the present process inregardA to the physical characteristics of theparticles. As hereinabovepointed out, however, kraft `pulp 4and the other paper industry fibersare relatively expensive to make and are decientchemicallyfor-applicants purpose because they do not contain the ligninsand desirable soluble materials v.of the original woodV structure. SuchVchemical deficiencies, of course-are not revealed in thephotomicrograph. n

A comparison vof Figures 5 and 7 reveals Vthat the fine fractionapproximatesl the quality offiber in kraftV pulp in regard to particlesizeand fiber characteristics through the elimination of the undesirablecoarsematerial illusvtrated in Figure 6. Thus, on a physical basis,thepresent product illustrated in'Figure 5 is comparable and almost equalto kraftpulp. On-a chemical basis, the product of 'Figure A5 is superiorto kraft pulp' by reasons of the inclusion of the lignins and watersoluble materials of the origv inal wood having thermoplastic and otherdesirable prop- 'erties which arefutilized to advantage in theprocessing of the fiber product for different purposes. Thusthe pres-1.ent product, illustrated in Figure'5,is superior not only to its ownsource materialfwhichwas in this case Asplund fiber, but is alsosuperiorfor many purposes to the rpaper industry pulp to which it bears a closephysical resemblanca Figure '2 illustrates an arrangemento'f-two'fractionating separators in seriesv to fractionate -theisourcematerial in two steps for'obtaining alfiner separation of the desiredfraction. `The sourcematerial S, which may be Asplund'fibenor any othermaterialY containing a desirable fiber fraction, either untreated ortreated with suit- `able additives, is introduced into the firstseparator B1. 4This separator is of the type illustrated at B in'Figurelwhich is capable of dividing the source material into two 'fractions ona coarseness basis, the products in Figure 2 being a first coarseproduct` C1 and a first 'fine product F1. The separatorB1 is adjustedinA accordance Vwith its capacity and the feed rate of source materialdelivered tof it to electf a clean separation of the-very'fcoarsematerial C1 with a negligible amount of the desirable fiber fractionincluded in the product C1. Such adjustmentY usually results in moreV orless coarse material being included in ,the fine product F1.

order to'rkeep .the fraction'F1 .containing the desiredfiber productasfree as possible f coarse material. There is operated at such a lowfeed rate as to be uneconomical,

andvimpractical. When this situation arises, the two-step fractionationprocess illustrated.in:Figure 2 facilitates a cleaner separation withless waste ofthe desirable ber product, while, at the same time,maintaining a satisfactory feed rate for steady economical commercialproduction.

Thus, in Figure 2, the first separator B1 may be considered as a rougherwhose ne product, F1, still containing a portion of the coarse fraction,is delivered as the source material to a second separator B2. Because ofits lower feed rate, the secondl separator B2 may be adjustedmorecritically toeect. av clean separation of the two. products. comprisingitsY fractions F2 and C2 without: objectionabley loss of thev desirablefiberY product in the rejected coarsematerial C2, In thisarrangement,the separator B2V can be adjusted to exclude all the remaining sticks,ribbons and thick ber bundles, and discharge in its product F2 onlytheultimate fibersV and slender flexible fiber bundles having thecharacteristics of ultimate fibers. In some cases this can beaccomplished using a smaller machine at B2 which increases4 the,yieldand quality of'the product over the single step processsufficiently to more than offset the additional costandoperatingexpense'of the second fractionator.

The series arrangement of Figure 2 can also be ernployed to produce anintermediate fraction substantially free of coarse bundles and also freeof ne broken fragments. In this case, the rst separator B1, instead offunctioning as a rougher, is adjusted to remove all the coarse materialat C1, leaving the desired intermediate fraction and the undesired linesto be discharged together in the product F1. The second separator B2 isthen adjusted to discharge the desired fiber product as a coarsefraction at C2, eliminating the dust and ne broken fragments as a rejectfraction at F2.

The particle size distribution of the source material will largelydetermine whether a one-step fractionation process is sufficient, orwhether one of the two different two-step processes just described willgive suiiiciently better results to justify the additional installation.Of course, to obviate the second separator B2, it is possible to feedthe product F1 through the separator B1 a second time, making anappropriate change in the adjustment of the separator for the reworkingand temporarily shutting off of the flow of new source material. It isalso possible to recirculate the product F1 through B1 along with thesteady flow of new material.

The arrangement shown in Figure 2, however, has the advantage that thetwo separators may be individually adjusted to produce the cleanestseparation for the purpose desired, taking into consideration thedifferent feed rates and the different ranges of particle sizedistribution in the two separators, the process being continuous anduninterrupted and requiring substantially no further adjustment aftersatisfactory steady operating conditions have once been established fora particular source material and feed rate.

Figure 3 is a longitudinal sectional view of a winnowing chamber whichmay be employed to separate a loosely uied fiber Source material, withor Without additives, into any desired number of fractions on acoarseness basis in a single operation. The elongated chamber,designrtcd generally at 85, is enclosed by opposite vertical side walls86 and a horizontal top wall 87. The input end of the chamber ispreferably closed by a vertical end wall 88, and the other end 89 may beleft open or enclosed and connected with a suitable air discharge duct;as shown. Nearthe upper end; ofthe.input-send;V the-wall188risaperturedto receive a horizontal'feediduct-fi 90. The bottomof the chamber 85 is dividedfinto a.

plurality of transverse bins atldifferent distances fromthe y feed duct90. kIn thepresent embodiment, these binsA comprise the series oftransverse conveyor belts 91 to 96, separated by transverse partitions97. The belts are arranged to remove the fractions separatelyv fromoneside of the winnowing chamber.

When the source material'Sisintroduced into an air stream from blower98in the feed duct 90, the material is blown longitudinally through thechamber S5 towards its open end-.89,' subject tothe inuencesof gravityand the propelling force of the air stream. The chamber 85 has a muchgreater. cross sectionalareathan the feed duct 90, andso |the velocitythrough the chamber is insuicient to carry thek soliclv materialindefinitely in air.

suspension, whereby the particles describe trajectories from theinput'duct 90'to.the different bins in the bottomof the chamber, asindicated by the falling material 99. The air velocity may bev adjustedto produce the trajectory pattern illustrated by controlling the speedof blower fan 98' or by the use of suitable dampers, not shown. Thelargest and heaviest particles, comprising the sticks and coarse fiberbundles, fall in the steepest trajectoriesinto therst bin 91, whereasthe dust and fine broken fragments fall in the attest trajectories,extending possibly eventothe last bin 96. Particles of intermediateVcoarseness fall in' the interveningV bins 92 to 95, whereby any numberof fractions may be obtained by dividing the lengthxof-thc chamberinto'a greater or lesser numben of bins;

The differenti types of apparatus i hereinaboveidescribed serve toillustrate a variety of means for carrying out the process of theinvention to obtain new and useful fiber products as set out in theobjects of the invention. The invention is not limited to these specifictypes of apparatus, however, but also includes such other devices andarrangements as may fall within the scope of the appended claims.

Having now described my invention and in what manner the same may beused, what I claim as new and desire to protect by Letters Patent is:

l. The method of continuously moving debered wood chips from a source ofsupply of same as a stream of fibers in a gaseous vehicle comprisingsteam, said stream of fibers containing a quantity of co-arse particlesand bundles of fibers of wood in admixture with individualized ultimatefibers of wood, continuously separating the said stream of fibers fromthe vehicular steam, rie-forming the stream of fibers, subjecting thefibers in a loosely liuffed condition to the inuences of gravity and amoving current of air in an environment allowing freedom of movement ofthe fibers in liow paths in different directions responsive to saidinfluences in accordance with the coarseness of the particles,collecting in one of said ow paths a relatively coarse fractioncomprising sticks and relatively massive fiber bundles, and collectingin another of said iiow paths a relatively fine fraction comprisingindividualized ultimate fibers and slender liexible bundles of ultimatefibers, and continuously conveying the particles of both fractions inmoving gaseous vehicle streams for further processing to produce aproduct consisting essentially of individualized ultimate fibers.

2. The method of continuously moving delibered wood chips from a sourceof supply of same as a stream of Wood fibers in an entraining gaseousvehicle comprising steam, said stream of fibers containing a quantity ofcoarse particles and bundles of fibers of wood in admixture withindividualized ultimate fibers of wood, continuously separating andremoving steam from the stream of fibers, reforming the stream offibers, continuously propelling heated air into the moving stream ofwood fibers, separating and removing spent heated air from the movingstream of wood fibers and entraining gaseous of fibers into a stream ofsaid coarse particles and bundles of fibers and a stream of saidindividualized ultimate' bers, continuously conveying the said separatedcoarse particles and bundles of bers in a moving gaseous vehicle streamfor further processing, and Ycontinuously conveying the separatedindividualized ultimate fibers in a moving gaseous vehicle stream toproduce a product consisting essentially of individualized ultimatebers.

'3. The method of Vclaim 2 in which a'portion of the separated spentheated air is recycled.

4. The method of continuously moving debered wood chips from a source ofsupply of same as a stream of wood bers in an entraining gaseous vehiclecomprising steam, said stream of bers containing a quantity of coarseparticles and bundles of fibers of wood in admixture with individualizedultimate bers of wood, continuously separating and removing steam fromthe stream of bers, continuously propelling heated air into'the movingstream of wood bers, continuously fractionating and dividing the streamof bers by subjecting the same to the combined inuences of gravity,centrifugal force, and air currents, into a stream of coarse particlesand bundles of bers and a stream of said individualized ultimate bers,conveying the said separated coarse particles and bundles of bers in amoving gaseous vehicle stream forY further-processing, and continuouslyconveying the stream of individualized ultimate bers in a moving gaseousYvehicle stream to produce a product consisting'essentally vehiclestream conveying the stream of individualized ultimate bers is a movingstream of heatedair.

12 6; The method of claim 4in which`V additional heated airisYcontinuously propelled into tl'te stream'of individf` ualizedultimatebers obtained after fractionation.`

7. The method of claim 6 iniwhich spent heated air is separated andremoved from the moving gaseous vehicle stream and the fractionatedindividualizedrultimate bers and a portion of Vsaidseparatedspentfheated air is recycled. Y i

8. VThe method'of `claim 4 in which spent heated air is separated andremoved from the moving stream'of entraining gaseous vehicle and woodbers just prior to the fractionation Vand dividing step.

9. The method of claim 8 in which a'portion ofthe separated spentYheated air is recycled.

References Cited in the le of this patent Y UNITED STATES PATENTSV Re.20,543

Crites Nov; 2, 1937v 1,574,384 Garner Feb. 23, 1926 1,577,545 Soderlundetal Mar. 23, 1926 1,897,620 Respess Feb. 14, 1933 2,090,955 Taylor Aug.24, 1937 2,325,055 Heritage July 27, 1943 2,405,213 Heritage Aug. 6,Y1946 2,420,036 Fairbairn May6, 1947 2,454,534 WalterY Nov. 23, 19482,540,348 Reed Feb. 6, 1951 2,553,412 Heritage May'15, 1951 Y MiscallJan. 27, 1953

